The ornamental design for a thermostat, as shown and described.
FIG. 1 is a front perspective view of a thermostat in accordance with a preferred embodiment of our design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a bottom plan view thereof;
FIG. 5 is a right side elevational view thereof; and,
FIG. 6 is a left side elevational view thereof.
The broken lines in the figures are for the purpose of showing environmental structure, are for illustrative purposes only, and form no part of the claimed design.
The rear elevational view of the thermostat is not shown in the drawings or described in the specification and, therefore, forms no part of the claimed design.